Burner assembly for space heater



Feb. 7, 1956 E. D. CADO ET AL 2,733,757

BURNER ASSEMBLY FOR SPACE HEATER Filed Aug. 19, 1952 5 Sheets-Sheet 1ilwenz oagi '11 $25- Early imm- Eds/Zak Feb. 7, 1956 E. D. CADO ET ALBURNER ASSEMBLY FOR SPACE HEATER 5 Sheets-Sheet 2 Filed Aug. 19, 1952Feb. 7. 1956 E. D. CADO ET AL 2,733,757

BURNER ASSEMBLY FOR SPACE HEATER Filed Aug. 19, 1952 5 Sheets-Sheet :5

oooooooooo oooooooooo i002 $55 51% #0156152 (2'. Seisaiu Feb. 7, 1956 E.D. CADO ET AL BURNER ASSEMBLY FOR SPACE HEATER 5 Sheets-Sheet 4 FiledAug. 19. 1952 Feb. 7, 1956 E, D. CADO ET AL 2,733,757

BURNER ASSEMBLY FOR SPACE HEATER Filed Aug. 19, 1952 5 Sheets-Sheet 5United States Patent BURNER ASSEMBLY FOR SPACE HEATER Erwin D. Cado,Chicago, Oliver B. Bushirk, La Grange, and Herschel A. Setser, Chicago,Ill, assignors to Motorola, Inc, Chicago, 111., a corporation ofIllinois Application August 19, 1952, Serial No. 3%,176

7 Claims. (Cl. 15853) The present invention relates to air space heatersof the type consuming liquid fuel such as gasoline or kerosense, andmore particularly to a burner assembly for use in such a heater enablingthe heater to provide adequate heat for a space of moderate size such asa house or a cottage.

The major requirements for heaters of the above-mentioned type are thatthey be inconspicuously small, have a. compact, simple and relativelyinexpensive construction, and be capable of generating adequate heat.Liquid fuel burning heaters are known to the art in which a volume ofliquid fuel is burned directly at its surface or is fed by a wick to acombustion chamber. This type of heater is not generally satisfactoryfor the abovementioned purpose because the burner structure is large inproportion to the heat obtainable therefrom, and the burner usuallyrequires a chimney to create the necessary draft. Another type of knownliquid fuel burner is one in which liquid fuel is atomized by a highpressure air jet prior to its application to the combustion chamber.This produces a combustible spray of fuel in the combustion chamber thatmay be ignited to effectuate the heating process. However, the latterarrangement requires a relatively large amount of power to carry out theatomizing process and is practical only in large installations. Yetanother type of liquid fuel burner is known in which the fuel isvaporized and mixed with air in a heated conditioning chamber prior toignition. A combustible mixture is formed in the conditioning chamberwhich is supplied to the burner ports adjacent the combustion chamber ofthe heater to be ignited and burned. This arrangement is advantageoussince the power requirement is low, its efliciency is high, and itsnecessary components are relatively simple and inexpensive and may bearranged in a compact assembly. However, although such a heater has beenused to some extent in automobiles and other vehicles, its use fordomestic and household purposes has been rather limited due to therelatively high heat requirements of the latter. It is also preferablefor domestic requirements to use a low volatile fuel such as kersosenerather than gasoline, and this has aggravated the problem since suchfuels have a certain maximum vaporization temperature and it has proveddifficult to maintain that temperature within the conditioning chamberand yet provide sufficient heat to the space to be heated.

Copending application Serial No. 52,169, filed October 1, 1948, in thename of Stanley J. Budlane, entitled Heater, and assigned to the presentassignee, which issued as Patent 2,673,558 on March 30, 1954, disclosesand claims a heater utilizing the afore-described vaporizing principlesof fuel conditioning, and which is constructed to overcome theafore-mentioned problems so as to be eminently suitable for householdpurposes. The heater disclosed in the Budlaneapplication achieves arelatively stable temperature for fuel vaporization and produces a highamount of heat even though a low R 2,733,757 Patented Feb. 7, 1956 'icevolatile fuel is used. The fuel conditioning chamber in the Budlanearrangement is maintained at the optimum vaporization temperature forthe particular fuel utilized by redirecting a pilot flame, normally usedto ignite the main burners, back against the conditioning chamber.Moreover, in order that the temperature of the conditioning chamber willnot exceed the optimum vaporizing temperature of the fuel utilized, asone or more main burners are brought into operation, the heater isconstructed so that heat from the main burners is directed away from thefuel conditioning chamber and that chamber continues to derive its heatsolely from the pilot flame. However, it has been found in the Budlanearrangement that under some conditions it is difiicult to insulatecompletely the conditioning chamber from the main burners so as tomaintain the chamber at the optimum vaporizing temperature when the mainburners are in operation.

The present invention constitutes an improvement over the arrangementdisclosed in the Budlane application, and its principal object is toprovide an improved burner assembly for a liquid fuel consuming heaterwhich is constructed so that even though the temperature of theconditioning chamber exceeds the optimum vaporizing temperature for thefuel utilized when the heater is in operation, the burner assembly is soconstructed that fuel vaporization continues to be carried on at theoptimum temperature and fuel sputtering and cracking is prevented.

A general object of the invention is to provide anew and improved burnerassembly for use in a fuel burning air heater which may utilize a lowvolatile fuel, and which enables the heater to generate more heat thanhas been heretofore considered possible without adversely affecting thevaporizing process of the fuel.

The features of the invention which are believed to be new are set forthwith particularity in the appended claims. The invention itself,however, together with further objects and advantages thereof, may bestbe understood by reference to the following description when taken inconjunction with the accompanying drawings in which:

Fig. 1 shows the complete heater unit mounted in an appropriate casing;

Fig. 2 shows a front view of the heater with the housing removed;

Fig. 3 shows a side view of the heater partially in section;

Fig. 4 is a top view of the heater;

Fig. 5 is a sectional view of the burner assembly of the heater takenalong the line 5-5 of Fig. 3;

Fig. 6 is a sectional view of a component of the burner assembly takenalong the line 66 of Fig. 5;

Fig. 7 is a front view of a vaporizing block used in the burnerassembly;

Fig. 8 is a sectional view of the vaporizing block taken along the line88 of Fig. 7;

Fig. 9 is a temperature-equalizing plate utilized in the burnerassembly;

Fig. 10 is a top view of the plate shown in Fig. 9;

Fig. 11 is a side View, partially in section, of the heater unit showingonly certain components of the heater; and

Figs. 12 and 13, respectively, show perspective and front views of arefractory unit utilized in the burner assembly.

The burner assembly of this invention is for use in a fuel burning airheater and includes in combination a heat conductive body having atleast one main fuel vaporizing passage extending therethroughterminating at the port adjacent the main burner port. A refractory unitengages the front of the aforesaid body and has at least one combustionpassage extending therethrough along a transverse axis with respect tothe front of the body, and also has an inner wall facing the pilotburner port and spaced from the front of the body to define with thefront of the body and with the sides of the refractory unit a baffiechamber. The wall in the refractory unit has an opening therein facingthe main burner port and communicating with the combustion passage.Finally, a heat conductive secondary fuel vaporizing shelf member isdisposed within each of the fuel vaporizing passages but heat-insulatedfrom the aforesaid body so that a temperature differential existsbetween each shelf and the body. The liquid fuel is supplied to thesecondary fuel vaporizing shelves and efficient vaporization is achievedin a manner to be described, even though the temperature of theaforesaid body and of the surfaces of the fuel vaporizing passagesthemselves exceed the optimum vaporizing temperature of the, fuelutilized.

As shown in Fig. 1, the heater is enclosed in a steel cabinet 10, whichhas a baked enamel finish on its outer surface. Circulating air inletlouvers 11 are formed at each side of the cabinet and at the bottom, andthese louvers are preferably equipped with aluminum-mesh air filtersinside the cabinet. A circulating air outlet louver 12 is formed in thetop of the cabinet. Circulating air is drawn in through the inletlouvers, heated and forced out through the outlet louver in a manner tobe described. The unit also includes a temperature control knob 13 atthe top, and also a humidifier cap 14 through which water may be pouredinto a humidifier can mounted in the interior of the housing 10.

With reference now primarily to Figs. 2-5, the heater unit includes avertical mounting plate 15 adapted to be supported by a wall or thelike. A horizontal shelf 16 having a central orifice 16a is supported bythe mounting plate, and an air circulating fan 17 is disposed in theorifice. As disclosed and claimed in copending application Serial No.305,132 filed August 19, 1952, in the name of Edward A. Salners et al.entitled Liquid Fuel Burning Heater Assembly, and assigned to thepresent assignee, fan 17 is supported and driven by a verticallydisposed motor 18 supported on a mounting bracket 19 which. in turn, isrigidly supported on the top of a cylindrical combustion fanhousing 20by studs 21a, 21b

and 21c. Housing 20 contains a combustion air fan 17a which is alsosupported and driven by motor 18. The

bottom of housing 20 is flat with a central aperturethrough which thecombustion 'fan draws the air to be supplied to the heater assemblyportion of the heater. Housing 20 rests on a shock mount 22 and furthershock mounts (not shown) resting in brackets such as bracket 23 securedto a cylindrical air header 24. The air header is supported by mountingplate 15 and communicates with an inlet air duct secured to andextending down the back of the mounting plate. Header 24 has anapertured top portion and is flexibly coupled to the aperture or orificein the bottom of housing 20 by means of a flexible coupling comprising apair of annular members 25a, 26in respective frictional engagement withthe orifices in housing 20 and header 24. Members 25a and 26 areintercoupled by an airtight flexible bellows 27' extending therebetween.Housing 20 is also flexibly coupled to a transition piece 28 rigidlysecured to mounting plate 15, and communicating through the mountingplate with a further duct 33 leading up the back of the plate adjacentduct 25 to the combustion assembly of the heater. The housing 20,therefore, provides a floating mounting for motor 18 so that vibrationsof the motor are not communicated to the assembly as a whole.

The heater includes a heat control unit 29 mounted to plate 15 belowshelf 16 and adjacent fan housing 20.

'The heat control unit includes a main switch for completing anenergizing circuit to the heater, and also into from a filter unit 46supported by the line.

eludes further switches controlling the application of fuel to the mainburners of the heater, the further switches being responsive to ambienttemperature variations and being set manually so as to establish adesired temperature within the space to be heated. Unit 29 is controlledby means of a control rod 30 rotatably supported on mounting plate 15 bya bracket 31 and extending to the unit from the aforementioned controlknob 13. The heat control unit is described in detail in aforementionedcopending application Serial No. 305,132 filed August 19, 1952, in thename of Edward A. Salners et al., entitled Liquid Fuel Burning HeaterAssembly, assigned to the present assignee, and a further descriptionherein is deemed unnecessary as this unit, per se, forms no part of thepresent invention.

The power supply unit for the heater is indicated generally as 32, andis supported by plate 15 below shelf 16 adjacent control unit 29.Details of the power supply unit and of the electrical connectionsthereto may also be found in the above-mentioned copending application.

A humidifier tank 35 is secured to plate 15. above the shelf 16 and hasan open top in communication with plug 14- of Fig. 1, so that water maybe added to the humidifier from time to time.

A rectangular shaped inlet air duct 36 extends through and is supportedby plate 15, and this duct communicates with transition piece 28 ofcombustion fan housing 20 by means of duct 33 secured to and extendingdown the back of plate 15 adjacent duct 25 as mentioned previouslyherein. A circular exhaust duct 37 also extends through and is supportedby plate 15, and the exhaust duct communicates with an exhaust pipe 37aextending from the back of the plate. A fuel metering unit base 38 issupported at the top of air duct 36 and has a series of solenoidoperated fuel metering valves 39-42 mounted thereon and extending intoits interior. A fuel pump 43 is supported on a bracket 44 extending fromthe back of base 38, and fuel such as kerosene, gasoline or the like issupplied to the pumpby a fuel line 45 extending there- The fuel issupplied to the filter unit by an inlet fuel line (not shown) extendingfrom the back of the filter and through mounting plate 15 to anappropriate fuel tank. A surge chamber 47 also communicates with filter46 and functions in well-known fashion. Fuel from the pump is suppliedby a line 48 to a pressure regulator 49, and fuel from the pressureregulator is supplied to the interior of base 59. The fuel metering unitand pump assembly may be similar to that disclosed in copendingapplication Serial No. 305,120 filed August 19, 1952, in the name ofJerome G. Zahradka entitled Heater, assigned to the present assignee,and a detailed description herein is deemed unnecessary.

The burner assembly of the heater is best shown in Fig. 3 and comprisesa vertical mounting plate supported by air duct 36 and exhaust duct 37.A casting 61 is secured to mounting plate 6 0 and surrounds the end ofair inlet duct 36. A fuel vaporizing block 62 of heat conductivematerial is secured to casting 61 with a temperature-equalizing plate,63 interposed therebetween, the temperature-equalizing plate and casting61 forming a plenum chamber 64 into which air from duct 36 is supplied.

Fuel vaporizing block 62 has a pair of parallel main fuel vaporizingpassages 65, and 66 extending therethrough one above the other andterminating respectively at the front of the block in main burner ports.67 and 68. The main burner fuel vaporizing passages and 66 communicatewith plenum chamber 64 through respective apertures 69 and 70 intemperature-equalizing plate 63 (Fig. 9). Vaporizing block 62 also has apilot burner fuel vaporizing passage 71 extendingv therethrough betweenthe main burner passages, the pilot burner passage terminating in apilot burner port 72 at the. front of the block and communicating at theback of the block with plenum chamber 64, through a hole 73 intemperatureequalizing plate 63. The vaporizing block has furtherpassages 74 and 75 extending therethrough, for reasons to be explained,and terminating respectively in the front of the block in apertures 76and 77 and communicating with plenum chamber 64 through respectiveapertures 73 and 79 in plate 63. Vaporizing block 62 has still furtherpassages (Fig. 7) 80, 81 extending from the front of the block part waytherethrough and then terminating at each side thereof (see also Fig.8).

Temperature-equalizing plate 63 supports a' series of shelves 82, 83 and84 which are disposed respectively in the main burner passages 65, 66and in the pilot burner passage 71 of burner block 62; these shelvesconstituting secondary vaporizing surfaces within these passages. Thesecondary vaporizing shelves are composed of a heat conductive materialsuch as a nickel alloy and are supported by plate 63. Plate 63 issandwiched between a pair of heat insulating gaskets 63a and 63b inorder that the shelves may be heat insulated to some extent from block62 so that a temperature diiferential is established between the shelvesand the surfaces of the passages, the temperature of the shelves beingequalized by plate 63. Each shelf has a multiplicity of apertures formedtherein with burred edges contacting the bottom surfaces of therespective passages.

An igniter unit 90 (Figs. and 11) is supported at one side of air duct36 in the inclined position shown in those figures. As shown in Fig. 6the igniter unit comprises a cylindrical housing 91 which communicateswith a tube 92 extending at right angles thereto and through a flamedirecting passage 93 in casting 61 and vaporizing block 62. Tube 92 alsoserves to support the igniter 9i), and further support is provided forthe igniter by a chamber 126 secured to air duct 36 and base 38. Chamber126 has an aperture 125 communicating with the interior of the air ductand an aperture 127 communicating with the interior of igniter 90. Theflame directing passage 93 terminates at the front of the vaporizingblock adjacent pilot burner port 72 as best shown in Fig. 7. Tube 92extends through an aperture 94 in temperature-equalizing plate 63 asshown in Fig. 9. As shown in Figs. 5 and 6, the igniter unit comprisesan electrical heating element 95 centrally disposed within a casing 96,the surface of the latter constituting a primary vaporizing surface forthe igniter. Electrical contact is made to the igniter element through astud 97 and the circuit is completed at the other end of the element bya strip 9%? connecting the element to casing 96 which is at groundpotential. casing 96 and may be composed of a nickel alloy or other heatconductive material which by virtue of its mesh construction is heatinsulated to some extent from casing 96 and maintained at a lowertemperature than the casing.

A solid refractory unit 166 (Fig. 3 and Figs. 12, 13) engages the frontof vaporizer block 62 and has a pair of spaced parallel combustionpassages 1121 and 132 extending therethrough one above the other alongtransverse axes with respect to the front of the vaporizing block. Therefractory unit has an inner wall 163 facing the pilot burner port 72and spaced from the front of the vaporizing block to define with thefront of the block and with the sides of the refractory unit a bafflechamber. The inner Wall has a pair of openings therein at the top andbottom thereof respectively facing main burner ports 67 and 68 and eachcommunicating with a different one of the combustion passages. 104, 165.In this manner, practically all the heat from the main burners isdirected into combustion passages 161 and 102 and has little effect onthe temperature of the vaporizing block 62.

As previously stated, fuel pump 43 supplies liquid fuel to base 38 ofthe fuel metering unit through pressure regulator 49. Liquid fuel fromthe interior of base 38 is supplied to igniter 96 through fuel line 116upon actua- ;.tion of solenoid valvel42. likewise, liquid fuel is sup- Amesh screen 97 surrounds a portion of "6 plied to the mainburnerpassages' 65 and 66 through fuel lines 111 and 112 upon actuationof solenoid valves 39 and 40 respectively, and to pilot burner passage71 9 through fuel line 113 upon actuation of solenoid valve 41.

The burner assembly is enclosed in a housing or casing 115 whichcommunicates with exhaust duct 37 as shown in Fig. 3. The casing alsosupports a heat exchanger 116 which extends laterally from either sideof the casing. Portions 116a and 11612 of the heat exchanger eachenclose a passage which communicates with passages 101 and 162 ofrefractory unit 190, and portions 116a and 116d of the heat exchangerenclose passages which communicate with the interior of casing 115 (Fig.6) and therefore with exhaust duct 37.

To place the heater unit in operation knob 13 is turned to an onposition which closes a main switch in unit 29 so that motor 13 isenergized and fans 17 and 17a are actuated. Fan 17 draws circulating airin through louvers 11 and drives it through orifice 16a in plate 16 uppast the heat exchanger 116 and out through outlet louvers 12. At thesame time, combustion fan 17a draws combustion air in through an airinlet pipe 36a which is mounted to the rear of the unit coaxially withexhaust pipe 37a, the combustion air being drawn down duct 25 intoheader 24 and forced out transition piece 28 up duct 33 and through airduct 36 into plenum chamber 64. Air from the plenum chamber is forcedthrough temperature-equalizing plate 63 to the main and pilot burnerpassages 65, 66 and 71 in vaporizing block 62. Air is also supplied toigniter unit 9% through aperture 125 in air duct 36 and through chamber126 into aperture 127 in casing 91 of the igniter unit. The igniterelectrical element is then energized so that primary vaporizing surface96 is heated, as is secondary vaporizing surface 97 which is constitutedby the aforementioned wire screen. Solenoid valve 42 is then energizedso that fuel is supplied to the igniter through fuel line 110. The fuelline terminates adjacent screen 97 so that fuelis dropped onto thescreen. When the igniter is in a relatively cool condition, the fuelpasses through the screen and is vaporized by the primary vaporizingsurface of casing 96. The vaporized fuel mixes with the air to form acombustible mixture which is ignited by electrically hcated strip 98 sothat an igniter flame is produced in tube 92 and in flame-directingpassage 93 in the vaporizing block 62 initially heating the block.Should surface 96 be heated beyond the optimum vaporizing temperature ofthe fuel used, screen 97 is heated to a lower temperature thereby due toits heat insulating relation with that surface, and the screen reaches avaporizing temperature so that the fuel is vaporized upon contacttherewith and does not reach surface 96., In this manner, the fuelcontinues to be vaporized at its optimum vaporizing temperature eventhough the heater element has caused surface 96 to exceed thattemperature.

When the flame in passageway 93 heats the vaporizing block to a selectedtemperature, solenoid 41 is energized so that fuel is supplied to pilotburner passage 71 through fuel line 113. The fuel line terminates atshelf 84 and when the vaporizing block is in a relatively coolcondition, the fuel passes through the apertures in the shelf to thebase of passage 71, which base constitutes a primary vaporizing surface.The apertures are formed in the shelves with burred edges preferably incontact with the bottom of the various passages to obviate the formationof fuel on the top of the shelves due to surface tension. The vaporizedfuel in the pilot burner passage is mixed with the air therein to form acombustible mixture at pilot burner port 72 which is ignited by theigniter flame from flame directing passage 93. The resulting flame fromthe pilot burner is directed against wall 103 of refractory unit andredirected thereby back against vaporizing block 62 and into passages74, 75, 80 and 81, so that the entire block is rapidly brought to theoptimum haust pipe 37a.

temperature for the fuel used. The igniter element may now bedeenergized and the igniter flame discontinued.

Fuel-metering solenoid valves 39 and 40 may now be energized and fuelsupplied onto shelves 82 and 83 in the main burner passages 65 and 66.The fuel passes through the apertures in shelves 82 and 83, and is vaporized at the base of the respective passages (which bases constituteprimary fuel vaporizing surfaces) and is mixed with air from plenumchamber 64. The resulting combustible mixture is ignited at the mainburner ports by the pilot flame, and the resulting main burner flamesare directed tangentially into combustion passages 101 and 102 in whicha swirling action is set up. The resulting combustion products aredirected through passages 116a and 11Gb of heat exchanger 116 and backto the interior of casing 115 through heat exchanger passages 115a and116d and, thence, out through exhaust duct 37 and ex- The actuation ofsolenoid valves 39 and 40 iscontrolled by unit 29 in the manner fullydescribed in the aforementioned copending application Serial No. 305,132filed August 19, 1952 in the name of Edward A. Salners et a1. entitledLiquid Fuel Burning Heater Assembly, so that the heater may be adjustedto maintain the space to be heated at any desired ambient temperature.

When the main burners have been in operation for some time, it ispossible under some circumstances (despite the configuration of unit100) for the temperature of the vaporizing block to rise above theoptimum vaporizing temperature of the fuel utilized. When that occurs,shelves 82, 83 and 84 are heated to such vaporizing temperature so thatfuel no longer passes through the'shelves to the primary vaporizingsurfaces, but is vaporized by the shelves themselves. In this manner,due to the temperature differential between the shelves and block 62,the fuel continues to be vaporized at its optimum vaporizing temperatureeven though the vaporizing block itself is at a higher temperature, andspluttering and cracking of the fuel is thereby prevented.

The invention provides, therefore, an improved heater unit havingextremely high heat capabilities and yet which operates with a highdegree of CffiClBHCY. By use of the present invention the heat output ofthe heater can be such that the temperature of the vaporizing blockrises above the optimum vaporizing temperature of the fuel utilized.'Yet, due to the action of secondary vaporizing shelves, the fuelcontinues to be vaporized at its optimum vaporizing temperature.Moreover, due to the configuration of the combustion chamber unit,maximum heat is obtained from the main burners with minimum I effect onthe vaporizing block.

While aparticular embodiment of the invention has been shown anddescribed, modifications may be made, and it is intended in the appendedclaims to cover all such modifications as fall within the true spiritand scope of the invention.

' We claim:

1. A burner assembly for use in a fuel burning air heater including incombination: a heat conductive block having at least one main fuelvaporizing passage extending therethrough terminating at the front ofsaid block in a main burner port, and having a pilot fuel vaporizingpassage extending therethrough and terminating at the front of saidblock in a pilot burner port adjacent said main burner port; means tosupply fuel and air to said main fuel vaporizing passage and to saidpilot fuel vaporizing passage; and a separate body engaging the front ofsaid block having at least one combustion passage extending therethroughspaced from the front of said block and along a transverse axis withrespect to the front of said block, and further having an inner wallbetween the coinbustion passage and the front of said block facing saidpilot burner-port and spaced from the front of said block to. definewith the front of said block and with the sides of said body a bafilechamber, and said wall having an opening therein facing said againburner port. and come municating with said combustion passage: wherebyfuel and air conducted through said pilot burner port are burned in saidbaffle chamber and fuel and air conducetd through said main burner portare burned in said combustion passage.

2. A burner assembly for use in a fuel burning air heater including incombination: a heat conductive block having a pair'of horizontal,parallel main fuel vaporizing passages extending therethrough mutuallyspaced one above the other and each terminating at the front of saidblock in a main burner port, and having a pilot fuel vaporizing passageextending therethrough parallel to and between said main burner passagesand terminating at the front of said block in a pilot burner portbetween said main burner ports; means to supply fuel and air to saidmain fuel vaporizing passages and to said pilot fuel vaporizing passage;and a separate refractory body engaging the front of said block having apair of spaced parallel combustion passages extending therethroughspaced from the front of said block one above the other along transverseaxes with respect to the front of said block, and further having aninner wall between said combustion passages and the front of said blockfacing said pilot burner port and spaced from the front of said block todefine with the front of said block and with the sides of said body abaffle chamber, and said wall having a pair of openings therein at thetop and bottom thereof respectively facing said rnain burner ports andeach communicating With a different one of said combustion passageswhereby fuel and air conducted through said pilot burner port are burnedin said baflle chamber and fuel and air conducted throu h said mainburner ports are burned in said combustion passages.

3. A burner assembly for use in a fuel burning air heater including incombination: a heat conductive block having at least one main fuelvaporizing passage extending therethrough terminating at the front ofsaid block in a main burner port and having a pilot fuel vaporizingpassage extending therethrough and terminating at the front of saidblock in a pilot burner port adjacent said main burner port; means tosupply air to said main fuel vaporizing passage and to said pilot fuelvaporizing passage; a separate refractory body engaging the front ofsaid block having at least one combustion passage extending therethroughspaced from the front of said block along a transverse axis with respectto the frontof said block, and further having an inner wall between saidcombustion passage and the front of said block facing said pilot burnerport and spaced from the front of said block to define with the front ofsaid block and With the sides of said body a baflie chamber, and saidwall having an opening therein facing said main burner port andcommunicating with said combustion passage; a heat conductive secondaryfuel-vaporizing shelf member disposed Within each of saidfuel-vaporizing passages and supported in heat insulated relation fromsaid block, and fuel supply means to introduce fuel on each of the shelfmembers so that vaporization of fuel permits a temperature differentialbetween said heat conductive block and said shelf member upon heating ofsaid block for eflicient combustion of fuel in said burner assembly.

4. A liquid-fuel burning air heater including in combination: a heatconductive body having at least one main fuel vaporizing passageextending therethrough terminating at the front of said body in a mainburner port, and having a pilot fuel vaporizing passage extendingtherethrough and terminating at the front of said body in a pilot burnerport adjacent said main burner port, the Walls of said passagesconstituting primary fuel-vaporizing surfaces; respective fuel linesextending to said passages for supplying liquid fuel thereto; means forsupplying air under pressure to said passages; and'a heat conductiveplate; heat insulating means for securing said plate to the back of saidbody in limited heat conductive rela tion therewith; heat conductiveapertured fuel vaporizing shelf members supported by said plate andrespectively I heater including in combination: a heat conductive blockhaving at least one main fuel vaporizing passage extending therethroughterminating at the front of said block in a main burner port, having apilot fuel vaporizing passage extending therethrough and terminating atthe front of said block in a pilot burner port adjacent said main burnerport, and further having an igniting flame directing passage extendingtherethrough and terminating adjacent said pilot burner port; a fuelconsuming igniter unit communicating with said flame-directing passage;respective fuel lines extending to said vaporizing passages and saidigniter unit for supplying liquid fuel thereto; means for supplying airunder pressure to said passages; and a separate refractory body engagingthe front of said block having at least one combustion passage extendingtherethrough spaced from the front of said block along a transverse axiswith respect to the front of said block, and further having an innerwall between said combustion passage and the front of said block facingsaid pilot burner port and spaced from the front of said block to definewith the front of said block and with the sides of said body a bafiiechamber, and said wall having an opening therein facing said main burnerport and communicating with said combustion passage.

6. A burner assembly for use in a liquid fuel burning air heaterincluding in combination: a Walled heat conductive body having aplurality of fuel vaporizing passages extending therethrough andterminating at the front of said body in respective burner ports, thewalls of said passages defining primary fuel-vaporizing surfaces; atemperature-equalizing plate means secured to the back of said body inlimited heat-conductive relation therewith, said plate having aperturesregistering with and forming inlets to said passages; means to supplyair to said vaporizing passages; a plurality of apertured heatconductive fuel vaporizing shelf members supported by said equalizingplate means and extending into said respective passages in spacedrelation with the respective primary fuel-vaporizing surfaces; and meansto introduce fuel on said shelf members to thereby maintain the shelfmembers at a lower temperature than said body clue to vaporization offuel thereon, so that vaporizing occurs at optimum temperature and fuelfrom said burner ports burns efiicientiy.

7. A burner assembly for use in a liquid fuel burning air heaterincluding in combination: a walled heat conductive body having at leastone fuel vaporizing passage extending therethrough and terminating atthe front of said body in a burner port, the walls of said passagedefining primary fuel-vaporizing surfaces; plate means; heat insulatingmeans for securing said plate means to the back of said body in limitedheat-conductive contact therewith, said plate means having aperturesregistering with and forming inlets to said passage; means to supply airto said vaporizing passage; a heat-conductive fuelvaporizing shelfmember supported by said plate means and extending into said passage inspaced relation with the primary fuel vaporizing surface; and means tointro duce fuel on said shelf member to thereby maintain the shelfmember at a lower temperature than said primary fuel vaporizing surfacedue tovaporization of fuel thereon, said shelf member constituting asecondary fuelvaporizing surface and having a multiplicity of aperturestherein to allow fuel to flow to said primary vaporizing surface whensaid secondary vaporizing surface is below the vaporizing temperatureand said multiplicity of apertures each having burred edges coactingwith the bottom of said passage to prevent the formation of excessliquid fuel on said shelf due to surface tension.

References Cited in the file of this patent UNITED STATES PATENTS437,310 McClary Sept. 30, 1890 700,275 Wilson Mar. 20, 1902 756,116Kengla Mar. 29, 1904 1,782,600 Brado Nov. 25, 1930 1,806,858 LivingstonMay 26, 1931 2,333,602 VanAlmelo Nov. 2, 1943 2,494,785 Tramontini etal. Jan. 17, 1950 2,540,018 Towar Ian. 30, 1951 2,588,349 Dusek et al.Mar. 11, 1952 2,617,399 Backus Nov. 11, 1952

